/*This is a simulation of the interaction of user programs with the OS to execut

Question

/*This is a simulation of the interaction of user programs with the OS to execute an I/O operation.

User programs will communicate with DOIO(OS) to request an I/O operation.(this will simulate a system call)

There should be one user running and it will execute 5 I/O operations. This program currently demonstrates

5 users running concurrently. How do I change this?*/

const int bufferSize = 5;

const int loopAmount = 25;

semaphore FULL1, FULL2, FULL3;

semaphore MUTEX1, MUTEX2, MUTEX3;

semaphore PRINT;

semaphore PIO, SIO;

semaphore operationComplete;

semaphore requestPending;

semaphore requestService[bufferSize];

int IORQid[bufferSize];

int IORQaddr[bufferSize];

int bufferAddress = 0, bufferID = 0, track = 0;

void User (int userID)

{

int i, j, address = 0;

for(j = 0; j < bufferSize; j++)

{

address = random(i+1) % 200;

p(FULL1);

p(MUTEX1);

bufferID = userID;

bufferAddress = address;

p(PRINT);

cout << "User " << userID + 1 << " executes system call SIO" << endl;

v(PRINT);

v(MUTEX1);

v(SIO);

p(requestService[userID]);

}

}

void DOIO()

{

int i = 0, tempID, tempAddr, index;

for (index = 0; index < loopAmount; index++)

{

p(SIO);

p(MUTEX1);

tempID = bufferID;

tempAddr = bufferAddress;

v(MUTEX1);

v(FULL1);

p(FULL2);

p(MUTEX2);

IORQid[i] = tempID;

IORQaddr[i] = tempAddr;

i = (i+1) % 5;

p(PRINT);

cout << "DOIO assembles IORB for user " << tempID + 1 <<

" and inserts it in IORQ" << endl;

v(PRINT);

v(MUTEX2);

v(requestPending);

}

}

void DeviceDriver()

{

int j = 0, driverAddress = 0, driverID = 0, i;

for (i = 0; i < loopAmount; i++)

{

p(requestPending);

p(MUTEX2);

driverID = IORQid[j];

driverAddress = IORQaddr[j];

j = (j+1) % 5;

v(MUTEX2);

v(FULL2);

p(FULL3);

p(MUTEX3);

track = driverAddress;

v(MUTEX3);

v(PIO);

p(PRINT);

cout << "Driver initiates I/O operation for user " << driverID + 1<< endl;

v(PRINT);

p(operationComplete);

v(requestService[driverID]);

p(PRINT);

cout << "Driver signal user " << driverID + 1 <<" to informed that I/O request is served."<< endl;

v(PRINT);

}

}

void Disk()

{

int i = 0, seek = 0, diskAddress = 0, j;

for (j = 0; j < loopAmount; j++)

{

p(PIO);

p(MUTEX3);

seek = track;

v(MUTEX3);

diskAddress = seek * 20;

for (i = 1; i <= diskAddress; i++){} //Dummy Loop

v(operationComplete);

p(PRINT);

cout << "Disk signal driver(operation complete)" << endl;

v(PRINT);

v(FULL3);

}

}

main ()

{

initialsem (MUTEX1, 1);

initialsem (MUTEX2, 1);

initialsem (MUTEX3, 1);

initialsem (PRINT,1);

initialsem (FULL1, 1);

initialsem (FULL2, 5);

initialsem (FULL3, 1);

initialsem (SIO, 0);

initialsem (PIO, 0);

initialsem (requestPending, 0);

initialsem (operationComplete, 0);

initialsem (requestService[0], 0);

initialsem (requestService[1], 0);

initialsem (requestService[2], 0);

initialsem (requestService[3], 0);

initialsem (requestService[4], 0);

cobegin

{

User(0);

User(1);

User(2);

User(3);

User(4);

DOIO();

DeviceDriver();

Disk();

}

}

Explanation / Answer

Modified Program

const int bufferSize = 5;

const int loopAmount = 5;

semaphore FULL1, FULL2, FULL3;

semaphore MUTEX1, MUTEX2, MUTEX3;

semaphore PRINT;

semaphore PIO, SIO;

semaphore operationComplete;

semaphore requestPending;

semaphore requestService[bufferSize];

int IORQid[bufferSize];

int IORQaddr[bufferSize];

int bufferAddress = 0, bufferID = 0, track = 0;

void User (int userID)

{

int i, j, address = 0;

for(j = 0; j < bufferSize; j++)

{

address = random(i+1) % 200;

p(FULL1);

p(MUTEX1);

bufferID = userID;

bufferAddress = address;

p(PRINT);

cout << "User " << userID + 1 << " executes system call SIO" << endl;

v(PRINT);

v(MUTEX1);

v(SIO);

p(requestService[userID]);

}

}

void DOIO()

{

int i = 0, tempID, tempAddr, index;

for (index = 0; index < loopAmount; index++)

{

p(SIO);

p(MUTEX1);

tempID = bufferID;

tempAddr = bufferAddress;

v(MUTEX1);

v(FULL1);

p(FULL2);

p(MUTEX2);

IORQid[i] = tempID;

IORQaddr[i] = tempAddr;

i = (i+1) % 5;

p(PRINT);

cout << "DOIO assembles IORB for user " << tempID + 1 <<

" and inserts it in IORQ" << endl;

v(PRINT);

v(MUTEX2);

v(requestPending);

}

}

void DeviceDriver()

{

int j = 0, driverAddress = 0, driverID = 0, i;

for (i = 0; i < loopAmount; i++)

{

p(requestPending);

p(MUTEX2);

driverID = IORQid[j];

driverAddress = IORQaddr[j];

j = (j+1) % 5;

v(MUTEX2);

v(FULL2);

p(FULL3);

p(MUTEX3);

track = driverAddress;

v(MUTEX3);

v(PIO);

p(PRINT);

cout << "Driver initiates I/O operation for user " << driverID + 1<< endl;

v(PRINT);

p(operationComplete);

v(requestService[driverID]);

p(PRINT);

cout << "Driver signal user " << driverID + 1 <<" to informed that I/O request is served."<< endl;

v(PRINT);

}

}

void Disk()

{

int i = 0, seek = 0, diskAddress = 0, j;

for (j = 0; j < loopAmount; j++)

{

p(PIO);

p(MUTEX3);

seek = track;

v(MUTEX3);

diskAddress = seek * 20;

for (i = 1; i <= diskAddress; i++){} //Dummy Loop

v(operationComplete);

p(PRINT);

cout << "Disk signal driver(operation complete)" << endl;

v(PRINT);

v(FULL3);

}

}

main ()

{

initialsem (MUTEX1, 1);

initialsem (MUTEX2, 1);

initialsem (MUTEX3, 1);

initialsem (PRINT,1);

initialsem (FULL1, 1);

initialsem (FULL2, 5);

initialsem (FULL3, 1);

initialsem (SIO, 0);

initialsem (PIO, 0);

initialsem (requestPending, 0);

initialsem (operationComplete, 0);

initialsem (requestService[0], 0);

initialsem (requestService[1], 0);

initialsem (requestService[2], 0);

initialsem (requestService[3], 0);

initialsem (requestService[4], 0);

cobegin

{

User(0);

DOIO();

DeviceDriver();

Disk();

}

}

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